Valve and hydraulic circuit therefor



Sept. 1s, 1951 B. WELTE 2,568,528

` VALVE AND HYDRAULIC CIRCUIT THEREFOR Filed Aug. 5, 1944 4 Sheets-Sheet l EL @i a. /l A3 l, ,un Hu [H HTTRNEYS.

sept. 18, 1951l B. WELT 2,568,528

VALVE AND HYDRAULIC' CIRCUIT THEREFOR H I H HI IH I' 40 s 5. Wn ./f ff# n ff ff 264 24; I N VEN TOR. .E 52mm/2f Wezfe.

Sept 18, 1951 B. WELTE 2,568,528

VALVE AND HYDRAULIC CIRCUIT THEREFOR Filed Aug. 5, 1944 4 Sheets-Sheet 4 kan ze;

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Patented Sept. 18, 1951 VALVE AND HYDRAULIC CIRCUIT THEREFOR Benedict Welte, Lake Orion Township, vOakland County, Mich., assigner to Colonial Breach Company, Detroit, Mich., a corporation of Delaware Application August 5, 1944, Serial No. 548,294 i The present invention relates to a multiple ow control valve mechanism for use in hydraulically operated machinery incorporating a constant displacement pump and two or more liquid passages to which the liquid discharged by the pump is supplied in succession, which mechanism serves to automatically and independently control the rate of flow through each passageway independently of the pressure and without subjecting the pump to any appreciable pressure in excess of that required to effect the desired rate of ow through each passageway.

It has been proposed that a plurality of constant displacement pumps of varying capacities be used singly or in various combinations during the operation of diiierent motors of a machine or during different portions of the movement of 16 Claims. (Cl. 137-166) one motor in order to control the speeds at which the motors operate, but such an arrangement is expensive, not only because of the cost of the additional pumps but because of the need for additional control means to throw the various pumps into and out of operation.

The speed of operation of several motors which are driven from a single positive displacement pump has also been controlled by means of bypass relief valves in combination with a throttle or restriction valve for each motor; but the difculty with such arrangements is that the pump must operate continuously against the pressure setting of the relief valve, which in turn must be the maximum pressure required for operating any of the motors. Since such high pressure is seldom required an excessive waste of power and heating of the liquid results. Likewise the speed of the motors varies with the mechanical resistance encountered.

Flow control valves have been used which, by means of a by-pass valve, transmit a xed volume of liquid per minute independent of the resistance offered by the operating motor. These valves are adjustable for ditlerent ow rates and have the advantage of maintaining a constant motor speed and automatically varying the discharge pressure of the pump to that required to maintain the motor in operation at the desired speed, thus reducing waste of power and heating of the liquid. However, prior valves of this type cannot be used to control the speed of two or more operating motors having diierent volumetric capacities, and many hydraulically operated machine tools and presses employ two or more motors of different capacities, nor can .they operate a single motor at two diterent speeds during different portions of its stroke. As

a result, if the flow control valve is set to maintain one of a plurality of motors at the desired speed the others will operate at improper speeds, and any adjustment to change the speed of operation, of the rst motor changes the speed of all motors.

In applicants copending application, Serial No. 495,856, led July 23, 1943, now Patent No. 2,395,702, dated February 26, 1946, is disclosed a now control system for three motors embodying a ow control valve of the type mentioned above, which controls the rate of :flow to the largest of the three motors, in combination with means for causing said valve to operate as an ordinary xed pressure-relief valve at a lower pressure during operation of the other two motors. This arrangement has the advantage of reducing the pump discharge pressure to a level below the usual overload or safety-relief valve pressure during the operation of auxiliary motors which do not require a high pressure, but it does not provide means to adjust the speed of the secondary motors and, moreover, the speed of those motors will vary with the resistance encountered.

Accordingly, it is the general object of this invention to provide several practical forms of a multiple flow control valve mechanism for use with a single constant displacement pump, which mechanism will automatically maintain the speed or rate of flow of liquid through each of a plurality of successively operated passageways at any desired level, subject to independent adjustment of the rate of now through each passageway, and which will automatically limit the discharge pressure of the pump to approximately that required to eiect the desired rate of flow through each passageway regardless of variations in the mechanical resistance oered to such iiow by the posiitve displacement motors connected to the passageways.

Other objects of the invention, which include the provision of such a ow control valve mechanism and control circuits therefor which are exceedingly simple in construction, :inexpensive to manufacture, and practical in operation, will become apparent from the following specication, the accompanying drawings, and the ap.- pended claims.

Figure 1 is a diagrammatic view of one form of the flow control valve mechanism.

Figure 2 is a fragmentary sectional view taken on the line 2-2 of Figure 1.

Figure 3 shows diagrammatically a modified form of the invention,

Figure 4 shows a lfurther modified form of the invention.

Figure 5 is a sectional view of one type of lowpass valve employed in the system illutrated in Figure 4.

Figure4 6l illustrates 'diagrammatically any application of the ow control mechanism to the operation of a single piston and cylinder unit in which an independent control of the speed of operation of the piston in each direction isY provided.

Figure '7 is a sectional view of a modified form of valve adapted to be used.v inthe.Y system illustrated in Figure 6.

Figure 8 illustrates diagrammatically a further modified form of the invention.

Figure 9 illustrates one of the. springgcentered four-way valves employed in the system illustrated in Figure 8.

Figure l0 is a diagrammatic illustration of a `further modification of the invention.

`Figure 11l isa sectional view of one of the valves employed in the mechanism of Figure 10.

Figure 12 is a sectional View of another of the valves which may 4be employed in the form of invention illustrated in Figure 10.

Referring to Figure 1 there is illustrated one example of a flow control mechanism adapted to{ controlthe rate of flow of liquid to each of ythree positive displacement motors, not shown. The mechanism includes a constant displacement pump I0 having an inlet conduit II communicating With a liquid reservoir I2. The detailed construction of the pump forms no part of the present invention but it should be understoodl that the invention is intended for use with constant displacement pumps; i. e., positive displacement pumps which deliver a constant volume of liquid for each unit of time.

The discharge outlet I3 of the pump is connected toan inlet port I4 of a4 valve housing I5. 'IlheY valve housing is formed with an interior generally cylindrical. chamber II4 in which is slidably` tteda. piston Il, fastened to a valve plunger I8. The valve plunger I8 controlsa discharge port I9Ywhichis connected by means. of a conduit 20; to the low pressure reservoir I2. PistonA IKT has an upward projection 22 of the saineV diameter as the plunger I8, and the entire plunger and piston element, including the proj'ection 2.2, is provided with a central bore '23. which extends throughout the unit. The projection 22iiits within a reduced cylindrical recess 2i4`in theY housing. The tapered end of the plunger is preferably tapered at a slightly greater anglev than that of the tapered seat, in accordance withV usual practice, so that the seating engagement occurs at the maximum diameter ofthe plunger. As a result of this arrangement thev piston and valve plunger unitis balanced against thevinuence of any pressure within the outlet portA I9 or the recess 24.

The upper side of the piston Il is subject to a downward force exerted by the spring 26 which normally actsv to hold the valve plunger I8, in the position in which it closes the outlet port I9. IILhe spring 26 is preferably of such stiffness that it will be overcome by a pressurel beneath the piston" I1, which is approximately twenty pounds suicient to note only that -thedifferential pressure required to overcome the spring 26 should preferably be a small proportion of the maximum operating pressure of the system. In addition, the design and arrangement of the spring, indicated only diagrammatically in Fig. 2, should be such that little change in the spring pressure occurs on movement oftheplunger I8 from fully closed to fully open position.

The valve housing is provided with an outlet port 28 which is. in constant communication with the inlet port I4 and, consequently, with the outlet of the pump I0, regardless of the position of thevalve plunger I8. The outlet port in turn is connected' to three conduits 30, 3|, and 32 which are connected in series and which, in the particular embodiment illustrated, are of progressivelyreducedsize. Each of these three lines contains an adjustable throttle valve. Thus the line 30 contains a throttle valve 33, the line 3| contains a throttle valve 34, and the line 3f2i'contains:l a throttle valve 35. Thesethree valves are identical' in construction, although also of progressively reduced' size,l and hencf a description of the internal construction ofthe valve 33 will'suii'iceior all.

Asbest shown in Figures 1 and 2,v thevalve. 33 comprises a housing containing a generally cylindrical rotatable plug 35; the rotative posi.- tion of which may beadjustedby handle:- 311. The plug 36; is provided intermediateits ends with a circumferentialgroove 38, which extends almost but not entirely aroundi the circumference of the plug 3.6i and which isjof.r progressively diminishing depth. Asya result'of thisl arrange.- ment, counterclockwise rotation of the valve plug` 3&1, as viewedin Figure 2, will progressively diminish the aperture for passage. or, fluid from the inlet toI the: outlet portof the.l valve. The groove 38r is sov proportioned-,as-y toprovide a rel.- atively' small resistance` toi the: flow, and the configuration is such,r that it provides smooth, Vzenturililie WY passages; and'V hence: maybe regarded as an adjustableVenturi opening.- It should' be understood. that. the' particularf form of'. adjustable throttle valve, while preferred, is not necessary to *theA invention, as.- onyl form of adjustable throttle: valve, o r in; some eases even a fixed' restrictiom may be employed.

Theex-tremityofyl e532 'isl connected by vmeans oa smallI pipe line; 39f'to` the` Valvechamber IB atfa point located' above the piston Il, thus-sub,- jecting the uppers side; of. the pistonl I'I to; the pressure existing.v inthe system, beyond the. three adjustablezrestriction; valves: 33; 3A,l and 35.'

Three branclr lines A0,. dlg, and 42": arev connected respectively^- tofthet. linesk 30',` 3,=I-,y andA 32; at points beyond the adjustable. restriction; valves in thelatter'lines'. The three lines 4.0; dil, and;42 may bevconnected'in-anysuitable manner tothree operating motorsof. thehydraulic system.- It is essential tothe successfull operation. of" the pres'.- ent invention that the hydraulicsystem, in which the present multipleiiow` control'` mechanisml is employed; incorporate-meansto insurefthat normal flow-occurs in only one .of the lines-40', 41Ir, and 42 ata time. AsA a generalv rulethiswill be Vaccomplishedl by blockingvalves, the nature and sequence of operation of which will depend upon the particular machine*l in which the system is employed. However, itmay be accomplished in any other: manner, asthereinafter indicated;

For-thepurposes ofi illustration there is shown in Figure 1 Iv` `a single three-position, solenoid-operated-valve which is'- eiectivefto per-mit now throughonly' oneof tlie-.lines-lll);` 4I, and? 12T-lat: a

. the line 39 exceeds a safe value.

time. This valve includes a housing 43 provided with three pressure ports 44, 45, and 46 connected respectively to the lines 4D, 4|, and 42, and three outlet ports 41, 48, and 49, which may be connected respectively to three operating motors of the system. The valve is provided with a spool, indicated generally at 50, having a plurality of lands 5I, 52, 53, 54, and 55. The spool is provided With a conventional spring centering device comprising a pair of annular Washers 56 and 51, which are forced apart by spring 58. Since the washer 53 bears against a shoulder 59 in the housing and against the spool 55, and the washer 51 bears against the end wall 60 of the housing and a shoulder 6| on the valve spool, the washers and spring serve to hold the valve spool in the central Vposition illustrated. In this position line 4I is in communication with line 48, line 40 is blocked by land 52, and line 42 is blocked by land 54. At the same time the motor line 41 is connected to a line 62 while the motor line 49 is connected to a line 63. The lines 62 and 63 in turn are connected to the low-pressure reservoir I2.

When the solenoid 65 is energized the spool 5|) is shifted to the right to a position in which line 4| is blocked by reason of the fact that the land 53 blocks the motor line 48 which is the only outlet in communication with the inlet port 45. Line 42 remains blocked by spool 54, but line 4D is connected to the motor line 41. At this time the motor line 48 is connected to the tank line 66. When the spool is shifted to the left by energizing solenoid 61, line 42 is connected to the motor line 49, line 4| is blocked by spool 54, and line 49 is blocked by spools 52 and 53.- At the same time line 41 remains connected to the low pressure line 62, line 48 is connected to the 10W pressure line 66 and the low pressure line 63 is blocked by land 55. It is apparent, therefore, that in each of the three positions of the spool two of the lines 40, 4|, and 42 are blocked and the motor lines associated with the blocked lines are connected to the low pressure valve reservoir. Drain passageways 64 are provided at each end of the valve to drain to the reservoir any liquid which leaks past the spools 5| or 55.

While not necessary to the present invention the pipe line 39 is preferably provided with a bleed restriction 10, and the housing of valve I5 is provided with a countersunk opening 1| communicating with the pipe line 39 but normally closed by means of a ball check valve 12 having a closing spring 13. The spring 13 is of such stiffness as to permit opening of the ball check valve 12 only after pressure in the pipe line 39 reaches the maximum safe pressure for the system. Thus in the particular example previously given, spring 13 would permit opening of the ball check valve 12 only when the pressure in the pipe line 39 exceeded a pressure in the order of 1000 pounds per square inch. The countersunk opening 1| is closed by means of a plug 14 provided with a conduit 15, which is connected to the low pressure reservoir I2. The combination of the ball check valve and the small bleed opening 16 enables the valve plunger I8 in the housing I5 to operate as a safety relief valve, inasmuch as it vents the liquid in the chamber I6 above the piston I1 to the low pressure reservoir when the pressure in During the relief action of the valve the bleed opening 10 insures that the pressure in line 39 will be less than that below piston I1 by an amount suflicient to overcome spring 26.

The mechanism disclosed in Figure l prt's inthe following manner. Fluid from the pump |0 flows through line |3, the valve I5 into the line 30 without restriction, as longI as any one of the motors connected with the lines 4I), 4|, and 42 is in operation. If it be assumed that the motor connected to line 40 is in operation and that the lines 4| and 42 are blocked, a pressure drop will occur as the iiuid iiows through the restriction valve 33, and consequently the pressure at the righthand side of the restriction will be less than that at the left. Since, under the conditions stated, there is no flow in lines 3| or 32 the pressure in line 39 Will be the same as that at the righthand side of the restriction valve 33 and, therefor-e, the difference in pressure at the opposite sides of the piston |1 will exactly equal the pressure drop across the valve 33. The restriction offered by the valve 33 when it is opened to its fullest extent is preferably such that the pressure drop caused by it for a iiow equal .reservoir I2, thereby reducing the quantity of liquid supplied through pipe 30, valve 33, and line 40. The position of the valve I8 Will automatically adjust itself to maintain a substantially constant pressure drop across the valve 33 and consequently the iiow of a substantially constant volume of liquid for each unit of time.

It should be noted that the valve mechanism automatically maintains a uniform rate of flow independent of the total pressure in line 40. Thus, if the motor to which line 4I) is connected is operating against a low resisting force, the pressure in line 4U may be quite low but the volume of liquid and the pressure drop across valve 33 will remain constant, and the pressure at the discharge of the pump Il! will only exceed the pressure in the line 4I] by the relatively small pressure drop across the valve 33. If the motor to which line 4|) is connected encounters a heavy resistance the pressure in that line will build up to that necessary to maintain the motor in operation at its fixed speed, and there will be no change in either the rate of flow of :fluid or in the pressure drop across the valve 33.. It is apparent, therefore, that the pump I0 is `only required to operate against that pressure necessary to operate the motor at its desired speed plus the small pressure drop across the valve 33.

It will be apparent that by adjusting the position of the plug 36 in valve 33 the size of the restricted opening may be varied and consequently the quantity of fluid for the fixed pressure drop correspondingly varied. Adjustment of the valve, therefore, provides a simple method of adjusting the speed of the motor connected to line 40. Y

If it be assumed that lines 40 and 42 are blocked and that fluid is iiowing through line 4 I, it is apparent that the pressure in line 3| at the righthand sideof restriction valve 34 will be equal to the Vpressure delivered by the pump less the total pressure drop through the restriction valves 33 and 34. The pressure in line 3| at the right# hand side of valve 34 is transmitted without change through line 32, valve 35, and pipe 39 to thaupperfend of'fthei valve chamber |;6.b.ecause 0f the: factA that. no. dow is occurring; through the: valvei. Consequently, the apparatus. willffuncf. lion asv before to maintain aixed pressure` drop across the'y valves 33 and 3.4; and consequently a. uniformflow of. fluid throushfthe line 4|.

. It is apparent that the rate of ow of liquid; through the line 4| may beadiusted by adjust;-` ng; the degree of openingzof throttle valve 3`4, withoutV changing the adjustment on. valve.b 3.a or airecting; flow through line 4|). when` that line. isoperating, so. longas the quantity-of fluid-.required inline 4| is. less than that` required-,in

llfof.

1. When linesm. and 4| are. blocked andow is;.occurringv in line 42 the apparatus wlloperate as; before-to maintain a, constant. pressure drop across, the valves` 3'3,l 314, and.\3 .5 and consequent,.- l-y agconstant iiowof liquid through line |52. Here again; the. rate. of flowv throughline l1&2. may be .ad

justedby `adjusting the, position of the. block; in

valve 35 without any change.. in the. positions of valves 3.3 and. 34;, so long as the iiovr required for; line; 42. is less .than that; required for. either ofitheflines 40 and l.

The system.illustrated.in.Figure 1. is'of. particular utility; in cases where the. plurality of motors to beV operated: require progressively smaller rates of fluid flow since. otherwise. it would not be possible to make. an independent adjustmentior the; rate, of. speed of each motor. So long :as the'. motors requirepdiierent .rates of flow and they. are connected tothe outlet. port. 23 of valve. I5in such manner-that the motor. requiring-,the greatestzow is .connected..first, Ythe motor requiring the next greatest ilow next, and so on, it is possible.` to. independently adjust. the speed of each motor by suitable. manipulationof the 'valves 33, 34, and 3.5. .Y

It will be. observedthat if the; quantity of vfluid required inline 4| is suilicient tocauseanappreciablepressure dropin passage through the valve 3.3, any adjustment of the.. valve; 3.3 which is prompted by the need to adjust ow inline 40 will effect. the quanttyof fluid supplied .toline 4l when the line is in operation. Consequently, in that case anyk adjustment ofithe position of valve 3,3fwill require a reverseadjustment of the valve 3|l-if no change is idesired Ain. the quantity of Iuid toV line 4|. The. sameistrue if the. quantity of uid required inline 132 is suicientto-cause an appreciable pressure drop ineither valve 33.201 valve Sd. ln some cases, therefore, it: may be necessary to manipulate. twoA or all three oi the throttle valves Vin order to adjust thefflowto one of --the operatingl motors. Accordingly, it isv preferred tofemploy the type or mechanismshown in;Figure 1 only in cases where the flow requirements of the severalmotors diiers toa very material degree. Thus, if for example, the. motor connected to lined@ requires eighty gallons of liquid ',perminute, the motor connectedytoline-.M requires twenty gallons per minute, and the vmo-v tor; connected to line ft2 requiresfivefgallons per minute, no appreciable pressure drop will occur through valves 33 and 34 when the motorschineeted tolinevilZ.. is, operating, Vand no appreciable pressure drop will'occurrin valve 93-whenthe motor connected to lineA 4l is operating'. Under these circumstances the speed of operation of each motor may be adjusted by adjusting the'pof sition of a single throttle valve without in any way affecting the speed of the other-three motors.

While in Figure. 1 a system is illustrated. for supplying three diierent operating motors, it will connected to thesystem in the same mannerby simply: extending the series lines 30s 35|., andff32l and providing one additional throttle valvefor.

each additional branch line. Itis only necessary` that the pipe line 39 be connected-to the` series, line beyond the last restriction valve. It. will-be apparent that. the flow control mechanisms of; FiguresY 1 through 5 would be ineiective if any ape preciable iiow occurred simultaneously in any two. of the branch lines 40., M, and 42, because the. pressure drop through the restriction valves. would not. reflect. the. flow through either branch line. It is for that reason that the mechanism is applicable only to machines in which it is` deI sired to control the speed of successivelyl operat A ing motors. As a general rule, flow through only one of the branch lines at a time -vvill be achieved by the use of suitable selectively operable block. ing valves. However, if one or more of the mo.e tors. comprisesa positive displacement cylinder. and piston unit which engages a positive abute ment. at the end of its-working stroke, it is une` necessary to block flow to such motor by means of avalve during operation of other motors because no flowcould occur in any eventafter the abutment is engaged. Likewise, itis-not neces,- sary to entirely block all flow to yone motor when another motor is operating, so` long as the flow is so reducedthat it causes no appreciable'pres sure drop on passing through the restriction valves.

In order to facilitate adjustmentl of speed, it is desirable to employa system in which the speed of each operating motor may be adjusted by operation of a single throttle Valve without alteringl the speed of any of the other motors. The apparatus disclosed in Figure 1 willaccomplish that result only if the volume requirements of the different motors diier very materially. However, in Figure 3 is illustrated avmodied multiple flow control mechanism in which thisdesirable result is achieved even though twoof the three Voperating motors have volumetric capacities which do not differ materially and in which the third-operatingrmotor requires a volume of liquid materially in excess ofthat required by either of the other two.

Referring to Figure 3 there is disclosed a valve mechanism 80 which is identical in construction tothe valve mechanism incorporated in the house ing I5 of Figure 1. This valve, like that previ-v ously described, has an inlet port 8| which may be connected to a constant displacement pump and an outlet port. 82 controlled by a plunger 8.3 having a piston lwhichis normally urged downf- Wardly by a spring 85. The valve is provided with an outlet port 86. connected kto a conduit 81 in which is provided l a throttle control valve 88 identical in constructionfto have valve 33 in Fig.- ure 1. Connected in series with the conduit 81 is a conduit 89. A conduit 90 in open communication with the conduit 81 beyond the throttle valve 83v and leads to the largest operating motor of the machine. A pair -of branch con-.-

' duits 9| and 92. are connected :to the conduit 8 9 The particular means illus,-

` hydroelectric circuit disclosed copending application, serial No. 550,330 led concurrently herewith, now Patent No. 2,529,718, dated November 14, 1950. It is suiiicient to note land 91.` These valves have a normal spring cenltered position for the valve spool in which position Arthey block flow through lines 90, 9| and 92.

fWhen the solenoid 98 of valve 95 is energized,

yline 90 is connected to a line 99 which may lead to lone end of an operating motor and a line |00,

which is connected to the other end of the same l operating motor, is connected to a line which leads to the low pressure reservoir. When the solenoid |02 is operated, line 90 is connected to lline |00 andline 99 is connected to line |0|. Valves 96 and 91 operate in a similar manner. These valves may be of any desired or conventional construction. For example, they may be constructed in the manner illustrated in Fig. 9,

Vbreach machine having a moving worktable,.

these valves may be operated by means of the in applicants only that such circuit must so operate the valves 95, 96, and 91 or the machine must be of such character that at any one time no flow occurs in any two of the lines 90, 9|, and 92, or the flow in all but one of them must be so reduced that it will not cause any appreciable pressure drop across the restriction valve or valves.

In'some cases, as in the operation of certain broaching machines, one or more cylinders is operated in both directions to a point where it is stopped by a positive abutment, and the pressure is maintained on the cylinder to hold it in that position until it is to be returned. In such cases it is unnecessary to employ valves having a blocking position since flow to the cylinder is automatically blocked by the fact that the cylinder cannot move.` A four-way valve similar to that illustrated in Fig. 12 may be substituted for any one or more of the valves 95, 96, and 91 under these circumstances.

The space within the chamber of valve 80 above the piston 84 isconnected by means of a pipe line |04 containing a restricton |05 to a 10W-pass Y valve |09. The valve |09 has an internal cylindrical chamber |01 in which are formed a pair of `spaced circumferential grooves |08 and |09 that are connected to the pipe line |04 by means of a passageway 0. VThe chamber |01 contains a Valve spool having a pair of circumferential grooves I i I and I I2 which are spaced axially from each other. The left-hand spool groove is connected by means of a cross passage ||3 and a communicating axial passage ||4 to the space at the left-hand end of the spool, while the righthand spool groove ||2 is similarly connected to the space at the right-hand end of the spool by means of a cross passage IE6 and an axial passage |i1. The left-hand end of the valve chamber |01 is connected by means of a line |20 to the line 9| at a point beyond the adjustable throttle valve 93, and the right-hand end of the valve chamber I 01 is connected by means of a line |2| to the line 92 at a point beyond the adjustable throttle valve 94. The end plates of the valve chamber are centrally recessed at |22, and an 10 inward projection |23 of limited circumferential and radial extent acts as a stop to prevent the spool from entering the recess |22. Consequently, the entire end of the spool will be subject to the pressure applied at the adjacent end port regardless of the position of the spool.

If it be assumed that the lines 9| and 92 are blocked by means of the valves 96 and 91, or otherwise, and that ow is occurring in line 90, it will be apparent that the pressure in line 81 beyond the restriction valve 88 will be transmitted without any reduction through line 89, line 9|, and line |20 tothe low-pass valve |06. When the spool of valve 05 is in the left-hand position illustrated, the spool groove coincides with the position of the housing groove IIJLB and consequently the fluid pressure in line |20 is transmitted through the passageways ||4 and I3, and the passageway I0 to the line |04, which in turn is in communication with the chamber of valve at a point above the piston 84. Consequently, the apparatus will maintain the pressure drop across valve 88 and, therefore, the volume of iluid ilowing in line 90 at a constant value in the manner described in connection with the line 40 of the apparatus disclosed in Figure 1. The same result will be achieved if the spool of the low-pass Valve |06 is at the right-hand end of its stroke during flow at line 90. In that case the pressure in line 81 beyond the throttle valve 88 will be transmitted without any reduction through lines 89, 92, and I2| to the lowfpass valve |06. The spool of the valve |06 being in its right-hand position, in which position the grooves I2 and |09 lie opposite each other, the pressure in line |2| will be transmitted through passagewaysL I I 1, IIS, and I I0 to the pipe line |04.

If lines 90 and 9| are blocked by the valves and 96, or otherwise, and ow is occurring in line 92, it is apparent that the pressure drop through throttle valve 94 `will result in a lower pressure in line 92 beyond the throttle valve 94 than the pressure existing in line 9| below the throttle valve 93. Consequently, the spool of the low-pass valve |06 will shift to the right, cutting oir communication between lines |20 and |04 and connecting line |2|,to line |04. Thus the valve in housing 80 will respond to the pressure in line 92 and maintain the pressure drop across the line 94 and, therefore, the flow through the throttle valve 94 ata constant value.

When lines 90 and 92 are blocked and flow is occurring in line 9| the pressure drop through throttle valve 93 will result ina lower pressure existing in the line |20 and consequently the spool of the low-pass Valve |06 will shift to the position illustrated in the drawings in which` it connects the line |20 to the line |04; thus enabling the mechanism to maintain a constant pressure drop and, therefore, a constant rate of ilow through the throttle valve 93.

Inasmuch as the adjustable throttle valves 93 and 94 are connected in parallel it is apparent that adjustment of either of them will not aiect the line containing the other. This enables the operator to adjust the speed of each of the two smaller motors by manipulating a single corresponding throttle valve without the necessity of adjusting the other throttle valve. If the capacity of the motors connecting the two lines 9| and 92 is materially less than that required for the motor connected to line 90 then, as previously indicated, adjustments of throttle valve 88 for the purpose 0I adjusting the rate of flow through line 90 will 1:92a arefblocked, i: the :pressure transmittedY by zthe lines v|20 and1|2 |v tosthe .opposite ends of thetlcwepass ,valves |05. are equalran'dr.that,l.therefore,..the lspool ofvalve |05 will tend to .remain in the posi- ,tion-@last occupied. `However, thereis no: positive s'iorce holding itv in that position and'.- it might bez.I

- possible; iny the..event of vibration for Y it .toshift finto@an;interme'diateepostiion .in .which it :would zblock ccmmunicationfbetween line |04 andfboth .cftthcglines .1I-2 titand.A |;2'| Thisy wouldl renderv innoperativefthefow control forline with the. re-

t sult :that '.the I, motor connected to line 90 .would receiveithe full` displacement ofthe pump. YThis result .inayg` be avodedf byf incorporating afspring yprfessed` .detent in the valve to hol'd..=.the spool against 'movement ifrom t either .of fitsztwoA end :l

positions when .oppositexends ofthe spool are :subject tojthesame pressures or, as an :alternative rlllgemerlt; thervalveimay :be ,provided zwithca spring :inuethe .manner illustratedain :Figure 5 @in \corrfiection twithfthefsmlar lowfpass valve 05 Aszthereillustrated, thespooLof-.the vaiveffwhicn e de ntical.A in constrpctiontolthat: previouslyrde- .fghifttQfth-risht againstutheferce exertedebyxthe .Spring-i215 when ,thefiinwiisroccilrrinainLthe line Which is connected;toLthegrightfhand endof the `.Vlo-Wpass-;va 1ve. v-,The only fgunctioniof the spring is .toginsure thatft Vspool;remains-at one endgof Athe strokefvvhen{themressurefiatgopposite ends'of .the lowpass ,valve is egual.

It :willobeappareni-that ..when rit is desi-red -to `Voperate vonly ftwo motors having volumetric ...capacities which are :inst materially different,

be. employed ,by simply, omitting ,the .adju-stable A,throttle .valvey88 and thegbranch lineV |10.

InfsomeE ,cases it ;isdesir able torelievethe presksure .on ,the `.system,vs /then ,none -of the v,motors is operating `This may-bereadily'accomplished by 5o the mechanism .illustrated in Eigure f3 byfsimply Iv,connecting a.point ,in the -.--ch amber of .valve 80 .Which..is located aboyefthe piston* B4 tothe .-low pressure 4reservoir. As ,shown in .Figure -3, .this

.maybe `accomplished by a line |30 containinga .solenoid-operated ,blocking `,valve ,indicated `da lgrammatcally ;at .I3|. The ivalvegll normally blocks zlovv vthroughgfalye .|30 b utfwhen.the` solenoid 1.3.2 of Va1ve=l3| isenergizcd the ,valve-.opens A,and permits unrestrictednijow ,tothedow pressure reservoir. This Aventing of ,thespaceabove piston 84 causes the V,by-pass valve Vplunger v|53to open yfully and discharge allof the liquid from the pumpto the reservoir atlow pressure.

multiple low-control mechanism which may be `employed where four opera-ting motors arev present and whichthe-'speed adjustments of -each are entirely-independent :of `the vadjustments of .any of the .othersffregardless ofthe `.capacity ofl .theseveralmotors Invthisconst-ruction there is .provided a valve-;rnechanism indicated diagramma-tically a|;.s|;40, '.Which .is identical-in construc- Y.tion `andfmode .of foperation to .the mechanism ,will Valancaa pressure at tl'ie'..left-=`v -anfinletz| 4 I connected to apo'sitive displacement Vpump and a by-pass. discharge |42-Whichis vconynected to the 10W pressure reservoir. The .valve VValso has an outlet 'line |43 to which are vconnected ing respectively adjustable S throttle @valves --MS, |49, |50, and |5|. vThe lines |44'to |4`| inclusive .are connected to the respectively operating motors in any desired manner, `such as by means of spring-centered, solenoid-operated, foureway valves which block fflow in the spring-'centered t position and, as previouslyy indicated; thesefvalves -may `be -operated byfany suitable instrumentality effective to cause-'thefvalves to blo'ckfflowf through .allbut oneof thefourbranch l-ines atlaltirne. J'If-4 blocking tour-vvayvalvesrv are not-r employed it will be appreciated that'-someother'meansfm-ust wbe present-to block now-'inthe-rnotors-whose Vspeed-is not-being controlled,'or\of--so reducing thatfow thatit causes no'appreciable pressure drop -in passing through the adjustable throttle valves.

The control-'line |50, fwhich i is connected toi-the Y space Aabove =the -valve piston-in'valve 40, '-is connectedbymeans of a low-'pass valve |5| identical i in construction tothevalve f 06 of rFigure Bitosa pairoflines |52.v and |53. vLine |52 in-t-urns connected through'l-aloW-pass v4Valve |54 whichis .preferably identical inf'construction tonthevalve |06', vshown in Figure 5,'to -apair of l'lines'l55' and 456. Line |55 .is connected Vtothevconduit* |44 `beyond the'adjustable throttle valve |48, and line |56 is connected to the conduit *|45 beyond the .aujustab1ethrott1e van/e449. simuarly the une |53 is connected to a`lowpass valve |58 identical inl construction tothe-.valve |06', shown inFigure ofllines |59 and-|60. The line |59'is connected to l the conduit |46 beyond -therthrottle vvalve 50, and the line |60 is connected tothe conduit |41 Vbeyond the throttle valve 5 l It will be apparent Vfrom the above "that-"thc line, of thelfourlnes |55,-'|56, |59, and |60;which fis-connected to the conduit in whichow isoccurring, vWill be'subject to Valovver pressure thanthe -remaining Athree lines; that is to say, that the three lines connected-tothe blockedor substan- -tiallylcloclred` conduits Will vbesulojectto the` pump -dischargepressure whereas the line connectedkto the conduit in which flow is occurring will be subject to a-pressure Which-isless than the/pump discharge pressure by the'amountof `the pressure drop `through the adjustable restriction'va'lve'in lthat conduit.

The three 10W-pass valves |5|, |55, and "|58 automatically select vthcline containing the lowest pressure of the four and-transmit that pressure -to line |50, -thus'enabling the Valve |40 to `maintain the pressure drop and now at the ldesired constant value. Since the four adjustable =fthrottle=valves |48, |49, |50, and |5| areconnected :to the system inparallel, an adjustment of any one Vof them will have no effect upon the others 4but Willsimply change the flow in the line in whichit is positioned.

It ispreferred vto employ in the low-pass Valves '|54 and |58 a spring biasing vdevice as shown in liigure 5, inasmuch as the conduits connected'to the endscf these two 'low-pass valves will beat the samepressure when the conduit in which now is voccurring is one of the conduits connected to Y `the otherof the two low-pass Valves |54 and |58.

Since the conduits |52 and |53 connected to the .low-pass valve |5| will never be at the same pressureso long as the machine `is .in operation,..the

13 spring may be omitted in the low-pass valve II, if desired.

It will be understood that the operating motors employed with the multiple flow control mechanisms of the present invention may be any suitable form of positive displacement motor, the usual form being that of a piston and cylinder unit with either the piston or cylinder constituting the moving element and the other being stationary. Moreover it will be apparent that the motors may be single-acting motors with a spring or gravity return in which event they may be operated by either individual three-way valves or a composite multiple three-way valve such as that shown in Figure l, or they may be doubleacting cylinder and piston units operated by means of four-way valves, such as the valve 95 described in connection with Figure 3. Moreover, a double-acting piston and cylinder unit may, for purposes of the present invention, be considered two separate operating motors where an independent control is desired for the movement in each direction. Such an arrangement is illustrated in Figure 6.

Referring to Figure 6, there is illustrated a valve which is identical in construction and mode of operation to the Valve in housing I5 of Figure 1 and which has an inlet port |1|, a bypass discharge port |12 leading to the low-pressure reservoir, and an outlet port |13 connected f to a conduit |14. The constant displacement pump is, of course, connected to the inlet port |1| in the manner previously indica-ted. A pair of branch lines and |16 are connected to the conduit |14 and the branch lines contain, re-

spectively, adjustable throttle valves |11 and |18 of the type previously described. The control line |80, which leads to the space above the bypass valve piston in valve |10 is connected to a low-pass valve |8| identical to that illustrated in Figure 3, and the ends of the valve 8| inl turn are connected to a pair of conduits |82 and |83. Conduit |82 is connected to the line |15 at a point `beyond the adjustable throttle |11, and line |83 is connected to the line I 16 at a. point beyond the adjustable throttle valve |18.

Lines |15 and |16 are connected to a control valve |85, which is provided with a valvespool |86 and a pair of outlet ports |81 and |88. l Valve |85 also has an outlet |89 which is connected to the low-pressure reservoir and which communicates with a pair of interior channels in the valve housing located at the ends of the housing and indicated by the numerals |90 and |9|, the connection being effected by means of the longitudinal passageway indicated in dotted lines at |92. The valve spool is provided with three lands |93, |94, and |95 and is shifted by means of pilot pressure supplied to the ends of the valve housing by means of a pair of pilot lines |98 and |99.

When the valve spool |86 is in the position illustrated in the drawings, land |94 blocks flow through conduit |16, and ilow is permitted from `conduit |15 to conduit 200 which in turn is'connected to the lefthand end of a cylinder I The righthand end of a cylinder 20| is connected at this time to the low-pressure reservoir by means of a conduit 202, channel |9I, passageway |92, and the outlet line |89. When pilot pressure is applied to the righthand end of the spool |86 Athe spool is shifted to the left into a position in which the land |94 blocks flow through conduit 15, and flow is permitted through conduit |16 and conduit 202 to the righthand end of cyl- 14 inder 20|. At this time the lefthand end of the cylinder 20| is connected to the low-pressure reservoir by means of the line 200 and the outlet line |89. i

Cylinder 20| contains a piston 203 having a rod 204 which drives any suitable instrumentality indicated diagrammatically at 205. Means are indicated diagrammatically for automatically shifting the valve at each end of the stroke of piston 203. This means includes :a lug 206 secured to the moving element 205 and eiective at each end of the stroke of the piston to contact one of a pair of levers 201 and 208 which are connected by means of a link 209. The shaft on which the lever 201 is fixed, which shaft is indicated by the dotted line |I0, operates a rotary four-way valve indicated diagrammatically at 2|I. The valve 2|| has four ports; port 2|2 is connected to a source of liquid under pressure such as theconduit |14; port 2|`3 is connected to low-pressure reservoir; port 2|4 is connected to the line |98; and port 2|5 is connected to the line |99. When the lever 201 is in the position illustrated the ilow lines through the valve 2|| are as indicated in the solid lines 2I6 and 2|1. When the lug 208 strikes the lever 208 thus shifting levers 208 and 201 clockwise, valve 2|I is shifted into a position in which the flow lines are indicated by the dotted lines 2| 8 and` 2| 9.

Accordingly, with the parts in the positions illustrated in Figure 6, pilot pressure is supplied to the lefthand end of valve |85 through line |98 and :ports 2|4 and 2 I2 of the valve 2| I, while the righthand end of the valve |85 is connected to the low-pressure reservoir through line |99 at ports 2|1 and 2|3 of the valve 2|I. Consequently, the fluid under pressure is being supplied from the pump through valve |10, conduits |14 and |15, the adjustable throttle valve |11, valve |85, and line 200 to the lefthand end of cylinder 20| and the piston 203 is moving to the right. When the piston reaches the righthand end of its stroke, valve 2|| Will be shifted and the righthand end of the valve |85 will be connected to pilot pressure through line |99 and ports 2|4, 2|5, 2I1, and 2|2 of valve 2||, while the lefthand end of valve |85 will be connected to the low-pressure reservoir by line |98 at ports 2|4 and 2|3 of valve 2||.

It is apparent that there is provided, in accordance with Figure 6, a multiple flow control valve mechanism incorporating means for independently adjusting the speed of the stroke of a single piston and cylinder unit in each direction of movement and in which an adjustment of the speed of operation in one direction Will not affect the speed of operation in the other.

'Ihe apparatus disclosed in Figure 6 may be modied to eliminate the low-pass valve |8| and still `accomplish identically the same results by altering the construction of the Valve |05 in the manner illustrated in Figure 7. As there illustrated, the Valve |85 is provided with a spool |86' having three lands |96', |94', and |95'. The valve is provided with a pair of inlet ports which are connected to the lines |15' and |16', which correspond to the lines |15 and |16 of Figure 6, and a pair of outlet ports 200 and 202 which lead to opposite ends of the operating cylinder and thus correspond to the lines 200 and 202 of Figure 6. The valve is also provided with an outlet port |89', which is connected with the lowpressure reservoir. Pilot lines |98 and |99' are providedfor conducting the pilot pressure to op- 'crate ethe yvalve15in tha-manner previously indicatedein connection valve :|18 5.

ll/"alare E85' diners from valve-185 :in that the `former is provided with a pair of auxiliar-y-n pasisageways V220i and :222 which f are connected ydirectly 'to fall-ne L80', `Whichcorresponds to `the line `A580 1 in Figure 6. In addition the :land '-.I 94 sWidened-iand so arrangedthat when it ,blocks viiiovvith-rough line i116' it also` blocks now through -Im-e I222 -butleaves .lines VV15 and 220 .lin :uid communication v'with v-.the .line V290'.. When the .spool 3h86 -v-isf shifted `from its .-righthand position indicated to its flefthand position the ,land I 94 gli-locks frowthrough lines H5 `and 220 andprowildes huid-communication Abetvveen lines 222, JFIXB, and '-202'. With-.this exception valve |85' `:isidentical rinvconstruction and mode of -.operationetothe valve-I -85-of .Figure 6.

v vItisapparentthat` when valve of .Figure l Vis @employed the'pressure in the-controlline .180 ...will 1be .the pressure in the motorconduit in which new .is -ocx-:urr-i-ng since the Vvalve which isVA employed-to block the other .motori-ine :also-blocks communication between rthatmotor lineandY the branch 4of thecontrol line 1.80' associated .therewith.

By providing-blocking valves for the motor lines which .also .control the-connectionV between those `motor lines and vthe .control line vfor the :by-pass-valye itis possible vto vomit thethreelowipass valves .otherwise Vnecessary .in a .flow-control l,mechanism such as that. illustrated .in Figure 4. Such anearrangement fis illustrated .in Figures-8 :and.9 wherein ithe Ivalve \mechanism..23ll, which .corresponds .to the-mechanism .Within fthe hous- .1'

.ingl.5-. of Figure .1, is connected Vto anfoutlet con- ,fduit 23l v`having Vfour Abranch lines in which .are fprovided adjustable throttle .valves 236, 23.1, .238, fand-239 irespectively. .Flow vthrough the motor vlines52.3.2,.2373,2311L and 235 is controlled by...means of spring-centered .solenoid-.operated four-way val-ves 24u, -241., .262, and .2.43. The controlline .245 for -thevalve fmechanism 23.0 contains .the fusual bleed restriction indicated `diagrammaticallyatlliyand is provided with four Vbranches 'Q2-41 248, 249, .and/2.50 which lead respectively Ito .the valves..24ll, .2!ii,2li2, and 243'. vSincethe'lalt- :ter valvesare identical in construction a 'de- -scription of valve 242 Will suffice for all.

l.As .shown `best in Figure .9 the valve 24u includes ,alhou-sin-g having an`internal :generally cylindrical borecon-taining a spool 252 provided .with ,three lands253, 254, and 255. The motor lin-e 232 .is-.connected .to .an inletport 258 and the control branch line V.23T-.is connectedto an inlet port 259.

LWhenfthespool '252 is in its central positionillustrated in Figure 9, land 25A blocks the .ports 258 rand 259, Yand the spool is normally held in the il- -lustrated central position by means of `a spring .centering device indicated .generally at 260, `.which .is identical in construction to lthe spring centering device illustrated .in Figure -1. `The valve chamber is provided with a pair of -outlet 'ports 262 land 263 to Which are connected lines "264 and265 respectively, which may lead to op- `'posite ends of one ofthe operating motors. The `4valve chamber also is provided With-fa pair of ports-.i266 and 26.1 which are connected by :means fof -a passageway .26B vindicated in .dottedlines :Theport 261 is connected to a Eline 269 which Afleads to a low-pressure reservoir. Drain passages y25S and 25? are provided .to conduct to .thereservoir, through passageway 268, any 'liquid that leaks past spools 253 and :255, respectively.

energized :andthe .spool 25.2 shifted thereby to the right against the action of spring-centering device 26B,Y :that ports 258and v259 .will nloe-connected together and to the port 262, thus allowing fluid from the motor line 232 to .flow to lines :264. At the same-time line r255 is connected through ports 263 and 265, passageway v268 .and .port26'l to the low-pressure reservoir line ,26.9. Under these circumstances the control line 245 of .the valve 23.0 will be subject to the pressure in line .f1-232 at a point .beyond the adjustable Vthrottle valve 235, and all of the remaining branch control lines 243, 2M, and 250 Will :be blocked by .treason of the fact that the valves 241,242, and .243 will be in their spring-centered position. When the solenoid 27H is energized, the spool :252 is .shifted .in the reverse'direction :connecting ports 258 and 259 together vand .to the port 2:63., While .line 254 .will be connected to the V.10W-pres- 'sure reservoir through ports -2-62, '267, and `v`line .269. In this :position also all of the remaining tour-Way valves .244, 2li-2, and 24-3 will -be spring .center-edby lthe vcircuit control means of themachine. It will be understood that each ofthe valves 241, y242, and -243 is similiar in construc- :tion and mode of operation to the Valve 240.and that the outlets of each lead to opposite endsof `the .remaining operating motors of the system, respectively.

Thehfour-Way valves -of themultiple flow control mechanism of FigureS may be controlled by ,any suitable means which Will insure that now is permitted through .only one of the four-Way Avalves lat a time. The fsequence'of'the voperation ofthe various valves'will-depend upon the requirements of the rmachine .in vvhichthe apparatus is employed. It will also be understood that any desired number of branchmotor lines may lbe connected to the mainline 23.1. If only three .branch lines are employed the four-Way valves may .be noperated by means of the hydroelectric control circuit for a breaching machine illustrated in applicants -copending application, Serial No. .550.330, filed concurrently herewith.

If=one or more of the motors is operated against a positive abutment at both ends of itsestrokaor .ifvfthe .-oW-of Aliquid to any such motor yduring the period-in-Which the mechanism is controlling the .speed of another motor is so reduced by other means-that it causes noappreciable pressure drop l.across vthe adjustable throttle valve -for such motor, thefspri-ng .centering device `may be omitted ,from `the-four-vvay valve of Fig. 9 which is fas- :sociated with such motor, since `the valve need not have .a blocking position.

The control lines for .the-by-pass valve of .the .multiple lflow-control mechanism may 'also be Acontrolled by special-valves responsive .to the existence-of iiow .in .the motor lines. Such ow- .responsive valves will connect the motor line, which flow is occurring, to the main :controlgline of {the-system, and disconnect the control .line .from the motor line either upon a stoppage `of .ilowor 1.a predetermined decrease in the rate of Y now. :Such aY system is .illustrated more 'or .less .diagrammatically in Figures l0 and I2 inclusive.

Referring to Figure 10 there is .illustrated fa valve mechanism `280 similar to `the mechanism within lthehousing l5 of Figure l. The valve .mechanism 280 has 4an inlet line 28|, a lay-pass :discharge line 282,.and a main discharge line 283 .similar to the corresponding lines connected to housing |75 Figure 1. The valve .280 also has :a @control -line 284 :similar in construction and r.Itgis apparent that -when the solenoid 21.0 is 15 iunctionto theline vt9 oFigure 1. The control line 284 may include a bleed restriction indicated diagrammatically at 285, if desired.

The discharge line 283 may have any desired number of branch lines leading to the hydraulic motors of the machine in which the system is used. Three such lines, indicated at 285, 281, and 288, are illustrated in Figure 10. Each of these lines contains an adjustable restriction valve 289, 298, and 29| respectively, each similar to the restriction valve 33 of Figure 1, and the lines are connected to the inlet ports of iiowresponsive Valves 292, 293, and 294, respectively. The outlet ports of the flow-responsive Valves are in turn connected by lines 295, 296, and 291 to any suitable control valves for the three motors of `the system. The particular valves, illustrated diagrammatically in Figure and in section of Figure l2, are four-way valves 298, 299, and 388, each of which controls the passage of fluid under pressure to one end of a hydraulic motor and the discharge of iiuid from the opposite end.

The flow-responsive valves 292, 293, and 294 may be of any desired construction s0 long as they are effective to connect the branch control lines 38|, 382, and 383 to their respective branch motor lines when flow occurs in the latter. Thus, for example, the valve 292 must operate, when flow is occurring through the branch motor line 286, to` connect the branch control line 38| to the branch motor line 286, and it must serve to disconnect line 38| from line 289 when no ilow is occurring in the latter or when the flow in the latter falls below a predetermined amount. One

satisfactory valve for performing the foregoing functions is illustrated in section in Figure 11. It will be appreciated that all three of the iiowresponsive valves may be of identical construction.

Referring to Figure 11 the flow-responsive valve comprises a housing 384 having a generally cylindrical bore 385 in which is slidable a cylindrical valve element 386 adapted to control communication between the interior bore and both the discharge port 381 and the control line 39|. The valve element 386 is provided with a stem 398 of reduced diameter which engages the end plate 389 of the valve to limit movement of the valve element 383 toward the right, as viewed in the drawing, to the position there illustrated. The valve element 386 is normally held in the position illustrated, in which it completely closes the discharge port 381, by means of a relatively light spring 389, the tension of which may be adjusted by means of athreaded adjusting plug 3 8. The plug 3|8 is threaded into an opening in the end plate 3|| and may be locked in any desired adjusted position by means of a lock nut 3| 2. An internally threaded cap 3 |3 covers the end of the adjusting plug 3|0 and seals the valve housing.V The discharge port 381 is in constant communication with the left-hand end of the bore of the valve housing by means of a passageway 3M in the valve housing and a communicating passageway 3|5 in the end plate 3||. The inlet pipe 286 is in constant communication with the right-hand end of the bore of the valve housing by means 01"' a port 3|6. The control line 38| is connected to a port 3I1 which, in the normal or inoperative position of the valve, is closed by means of the valve element 388.

The valve 292 operates to permit substantially unrestricted flow from line 286 to line 295 by reason of the fact that the valve element 386 will automatically assume a position in which the pressure drop past the discharge port 381 is bal- 18:i anced by the force exerted by spring 389, and the latter spring is preferably made quite weak so that the valve will offer very little resistance to the flow. This operation results from the fact that the pressure at the discharge port 381 is in communication with the left-hand end of the valve element 386 and, consequently, the valve element is balanced except for the light force exerted by the spring 389. As a result of this arrangement, the element 388 will assume a position in which the pressure at its right-hand end. which is the pressure at the inlet port 3|6, exceeds the pressure at its left-hand end, which is the pressure at the outlet port 381, only by the amount necessary to overcome the spring 389. This action by the valve is vindependent of variations in the pressure in line 295 so long as the maximum operating pressure of the system is not reached. However, if line 295 is entirely blocked the valve element 386 will close the discharge port 301 because in the absence of flow no pressure drop can occur through the discharge port to i counterbalance the force of spring 389. The valve element 386, in closing discharge port 381, likewise closes port 3|1 connected to the branch control line 38|, thereby disconnecting that line from the motorline 286. The valve thus operates automatically to connect the branch control line to the motor line only when normal flow is occurring in the latter. Consequently, so long as `flow is occurring in only one motor line at a time the pressure in the main control line 284 will be that exiscting at a point beyond the restriction valve in the motor line in which flow is occurring, and the multiple flow-control mechanism will operate as previously described in connection with the earlier modiiications of the invention.

While the valves 298, 299, and 388 may be of any desired construction and may, for example, be spring centered blocking center four-way valves, like the valve illustrated in Fig. 9 (but omitting port 259 of the latter), it is not necessary that these Valves perform a blocking functionif other means are present to block or reduce ow through all lines except the one in which at any given time the rate of ow is being controlled. Thus, if one or more of the motors is operated against a positiveabutment at each end of its stroke, the valve may be constructed in the manner illustrated in Fig. 12.

As shown in Fig. l2, the valve 298 comprises a more or less conventional solenoid-operated four-way valve having a detent to retain it in either one of its two positions. The valve comprises a generally cylindrical body 328 having a cylindrical bore. The pressure line 295 is connected to a port 32|, and the valve is provided with two discharge ports 322 and 323 and a reservoir or return port 324. Positioned within the bore of the valve is a spool indicated generally at 326 having four lands 321, 328, 329, and 338. The land 338 is provided with a pair of axially spaced, V-shaped, annular grooves 33| and 332 adapted to co-operate with a spring-pressed detent which serves to hold the spool in either one of two axial positions of adjustment. In the position of the valve spool illustrated, port 32|. is in communication with port 322, and port 323 is in communication with return port 324. In addition, the return port is connected to the space between lands 329 and 338 by means of an annular groove 333 within the valve body and a. communicating passageway 334 shown in dotted lines in the drawing. The ends of thevalve housing are closed by means of end plates 335 and 336,v andthe spaces at the outer ends offthefspool thefleft, thereby-connecting portsv 32| and 323* andfconnecting 1oort5322-toy the reservoir or return port 324. In this position the detent 342 will enter groove 332 Ain the spoolf to hold it in its lefthand -KpositionzA Itwillbe noted'that in neither position does the valve block flow fromthe line 295 to the branch motor lines 322 and 323`Which mayleadto opposite ends'of the same pistonl and cylinder unit.

As previously indicated, the forms -of inventionillustrated in Figs.. 1 through 9 are eective to control -the speedof one motorl unit, even though atthe same time another` motor unit is, receiving a'small'quantityof liquid.` provided .theA

quantity is so small thatit does` not effect an appreciabl'epressure dropthrough its associated adjustable throttlevali/e.Y The mechanism of Figs.,

10 to 12 has the further advantage that it will operate satisfactorily,I even though a greater quan.- tity of liquid isiiowing to .oneofthe motors whose speed is Vnot being` controlled 'as long .pas that quantity is lessithan'the amount required by that motor when itsspeed is .being controlled by. the mechanism. This function results from thetfact that it isv possible, by ,selectingthe location of port 3|'|"ofvalve;292'Ielativeto the discharge port-301, to .cause the valve element.306 to block the ,Dort ,3|| before the discharge, port 3111 is closed." The arrangement ofthe ports may besochosenpthat port 3| is closed, while port 30.1' is.

open to any. desired degree less, than `the openin g which will occur during the period in which the motor associated with the valve is operated at a controlled;` speedV byY thermechanisrn `previously described. It willv be appreciated, however,. that asinthe prior modifications, the mech- 'P anism controls the speed of operationof only one motor. at a time, and consequently additional means. are required Lto restrict the flow through the lineto any motorduring the period ,in which the. speedof operation ofA another motor isY be.-

ingI controlled -by the, mechanism. Such` means Y may bea throttlevalve or. a .xed or moving abutment forthe motor..A

The iiow .controlrimechanisms of' the.present application ,are of, generalutility for use inany hydraulic. apparatus. incorporating a plurality of separate operating motors.-

In addition,raswilljbe-apparent, the multiple motor. lines` mayV bev connected to thevsame motor at different times ,inc order to. provide different rates .of now for. different portions of theI stroke ofthe same, motor., Insuchcase.. asingle motor may, ineffect,ac t asa ,plurality of successivelyA t. operated motors ofdifferentcapacites. The owcontrol,mechanismen-Figures V1 through, 10. andill.` may .bemanufactured and` sold for employment` in hydraulicA machinery generally, independent of the means employed in thelmachinf.

ery forselectively blocking thelines to the several` operating motors. For this purpose it is obvious that,ii` desired, themechanismincorporatedinf any of the mainA control valve-housingsl I5, 8|),y

|49, |10, or 280 may bfi-incorporated in a single casing with any or all of the adjustablethrottlev-` valves and the control valve lines for that valve,- including such low-pass valves4 or now-responsive valves as are required; The purchaser may then-'- simply connect the several motors to the outlets` provided in the housing v:and incorporate the nec-` essary blocking valves in the motor lines. These blocking valves may be operated by any desiredmeans either automatically in a desired sequence or manually or a combination of both; as thecharacter of the machine requires.

disclosed in connection with Figures'l to 9; inclusive, is not complete withoutv the blocking valves,`

and thus the blocking valves may either be incorporated in the same `housing with the remain*- ing structure or suitable additional ports mayA bel provided by which the purchaserV mayfconnectf the branch control lines from the blocking valves to the control passagesl in the housing. Certain@ of the claims recite means for selectively blocking flow through all but one of the branch-motorv lines at a time, or meansl for permitting, flowV through only one line at a time, orsimilar recit`ations. It will be understood that such rectations are intended to cover blockingmeans Ifor the inactive branches even though they do not block all flow, so long as they so reduce the quantity* of liquid flowing that it causes no appreciable pressure drop across any of the restriction valves through which it passes.

While inthe various modifications illustrated" and described the valve mechanism is shownemw` ployed in a hydraulic system in which the pump;- receives its supply of, liquid from a reservoir, itl

will be appreciated that in; certain types otsystemsthevarious hydraulic motors may discharge;`

directly to the intake of the-pumpwithout passing througha reservoir, if desired.

While several forms of the multiple'ow-control mechanism4 are illustrated and describedit` will be apparent that further variations in the arrangement and design of thefvarious parts of the mechanism may be indulged in within the spirit of the invention and-scope ofthe appended# claims. WhatV is claimed is:

1. Amultiple flow control valve mechanism for use in controlling the operation of a pluralityofv successively-operable fluid motors from afluidn pressure source consistingfof a constant displace-- ment pump, saidmechanism including a control valve having'a housingfcontaining avalve plungerl provided with a piston which divides the interior of the housing into two separate chambers, one of said housing chambers having an inlet portv adapted to be connected toa sourcegof fluidunderpressure and a low pressure discharge port, said discharge port being controlled by said plunger;A means defining a passageway leading from said inlet portto rthe other housing chamberfsaid' passageway containing a plurality of spaced restrictions. in series, the succeeding downstream restrictions being no greater in iiowV area thang the preceding restrictions, a spring` acting to cause said plunger to move in a direction to close said discharge port whenY the diierence in pressure between said chambers tends to fall below a predetermined amount, a plurality of outlet passageways connected to said rst mentioned pas- Y sageway, the points of.. connection of said outlet passageways with the first passageway being lo The type of multiple'ow controlmechanism? 2l' cated one beyond each of said restrictions in the direction of iiow, and means for selectively blocking ilow through all but one of said paths. V

2. A multiple flow control valve mechanism for use in controlling the operation of a plurality of successively operable iluid motors from a fluid pressure source consisting of a constant displacement pump, said mechanism including a control valve having a housing containing a valve plunger provided with a piston which divides the interior of the housing into two separate chambers, one of said housing chambers having an inlet port adapted to be connected to a source of' fluid under pressure and a low pressure discharge port, said discharge port being controlled by said plunger, means defining a passageway leading from said inlet port to the other housing chamber, said passageway containing a plurality of spaced restrictions in series, the succeeding downstream restrictions being no greater in iiow area than the preceding restrictions, a spring acting to cause said plunger to move in a direction to close said discharge port when the difference in pressure between said chambers tends to fall below a predetermined amount, and a plurality of outlet passageways connected to said first mentioned passageway, the points of connection of said'outlet passageways with the first passageway being located one beyond each of said restrictions in the direction of iiow.

3. A multiple now control valve mechanism for use in controlling the operation of a plurality of successively operable fluid motors from a fluid pressure source consisting of a constant displacement pump, including a control valve having a housing containing a valve plunger provided with a piston which divides the interior of the housing into two separate chambers, one of said housing chambers having an inlet port adapted to be connected to a source of uid under pressure and a low pressure discharge port, said discharge port being controlled by said plunger, means defining a passageway leading from said inlet port to the other housing chamber, said passageway containing a plurality of spaced restrictions in series, eachrestriction being of greater restrictive elect than the preceding restriction progressively along said passageway in a direction of liquid flow, a spring acting to cause said plunger to move in a direction to close said discharge port when the difference in pressure between said chambers tends to fall below a predetermined amount, and a plurality of outlet passageways connected to' said rst mentioned passageway, the points of connection of said outlet passageways with the first passageway being located one beyond each of said restrictions in the direction of the flow.

4. A multiple iiow control valve mechanism for use in controlling the operation of a plurality of successively operable iluid motors from a fluid pressure source consisting of a constant displacement pump, said mechanism including a housing having an inlet port and a by-pass valve for bypassing to low pressure a portion of the liquid which enters said inlet port, differential pressure means including a cylinder and piston for controlling the degreeof opening of said by-pass valve, a spring normally acting to close said bypass valve and effective to hold said valve closed against a predetermined differential pressure applied to said differential pressure means, means defining a plurality of conduit paths in constant i communication with said inlet port, a restriction in each conduit path defining a restricted opening of a size determined by the rate of flow del sired in said path, independent means for adu justing each of said restrictions means providing an open liquid communication between said inlet port and that side of the piston of the differential pressure means at which pressure tends to open the valve, and means associated with the conduit paths for subjecting the opposite side of said piston to the pressure existing beyond the restriction in the conduit path in which liquid flow is occurring and means for selectively blocking flow through all but one of said paths. Y

5. A multiple ow control valve mechanism for use in controlling the operation of a plurality of successively operable fluid motors from a fluid pressure source consisting of a constant displacement pump, said mechanism including a housing having an inlet port and a by-pass valve for bypassing to low pressure a portion of the liquid which enters said inlet port, differential pressure means including a cylinder and piston for controlling the degree of opening of said by-pass valve, a spring normally acting to close said bypass valve and effective to hold said valve closed against a predetermined differential pressure aplplied to said dilferential pressure means, means defining a plurality of conduit paths connected in parallel'in constant communication with said inlet port, a restriction in each conduit path, deflning a restricted opening of a size determined by f the rate of flow desired in said path, means providing Van open liquidcommunication between saidinlet port and that side of the piston of the differential pressure means at which pressure' tends to open the valve, and means associated with the conduit paths for subjecting the opposite side of said piston to the pressure existing beyond the restriction in the conduit path in which liquid flow is occurring and means for selectively blocking flow through all but one of said paths.

6. A multiple flow control valve mechanism for use in controlling the operation of a plurality of successively operable fluid motors from a iluid pressure source consisting of a constant displacement pump, said mechanism including a housing having an inlet port and a by-pass valve for bypassing to low pressure a portion of the liquidwhichventers said inlet port, differential pressure means including a cylinder and piston for controlling the degree of opening of said by-pass valve, a spring nomally acting to close said by" pass valve and effective to hold said valve closed against a predetermined dinerential pressure applied to said differential pressure means., means `defining a plurality of conduit paths in constant in the conduit path in which liquid flow is occurring.

'7. A multiple flow control valve mechanism for use-in controlling the operation of a plurality of successively operable fluid motors from a fluid pressure source consisting of a constant displacement pump, said mechanism including a housing hgaving an inlet port and a by-pass valve for by-passing to low pressure a portion of the liquid lwhich enters said inlet port, differential pressure means including `a cylinder and piston for controlling-the. 'degree-.of opening. of said .by'fpassf va'lvepafspringanormally actinggto closefsaidabyfpass valveandzeffective toy holdsaid valve closed againsiza.predetermineddifferential pressure applied-.tosaidfdifferential pressure means; means defining a plurality .of eonduit. paths connected' in-parallel in constant communication with said inlet-port; a: restriction inY eachV conduit path,

meansffor.independently adjusting said restrictions',.l means. providing an open `liquid `communication between. said in'l'etA port. andf that side` of thefpistonof the'differential pressure means at whichfpressure tends to open the valve, and means associated .with the conduit paths for subjectingfthe"opposite'sidefof said pistontothe pressure'.existingxbeyond the restriction in:the.

conduitpathiinwhich liquid flow is occurring.'

8Amultiple iiow control valve'mechanismfor use -witha fluid'pressure source consisting of. a

constantdisp'lacement pump, said mechanism `in*- cluding a housing having an inlet port and 'ahy-f passtzvalve for icy-passing to low pressureapor` tioniofv the 'liquid whichV enters saidrinletr'port;` differentialv pressure Vmeans .including `a cylinder and `pistonrforv controlling thefdegree of opening of'said Aluy-pass valve,A a spring normally actingVv toclosersaid icy-pass valve and effective to `hold saidivalve' closed against a predetermined differ-- ential: lpressurev applied to said differentialv presi suremeans, means definingra plurality- `of con'- duitfpaths in constant communication with said`V inlet port,..a restriction Vin each'conduit path' defining .arestricted opening of a size determined byxthe rate 'offlow' desired insaid path; means for independently adjusting said4 restrictions, means providing an open liquid communicationrbetween said inlet port-and that sideof'the pistonv of the; differential 'pressurer means at which pressure tends-to .open 'ther valve-means ,for selectively blocking ow through all but one of saidlpaths; and 'means associated withthe conduit paths for subjectingtheropposite side of said pistonztothe pressure existing. beyondv the restrictionintthef path vthrough :which liquid flow is occurring.`

ELIA-multiple flow controlvalve mechanism for use.A with a1 fluid: pressure source consisting of a' constant displacement pump, said'mechanism including1 a housing havingv an. inlet port 'and a by-pass-valve `for by`passing to low pressurea portionof the liquid `which enters Vsaid inlet port;

. close said by-.passvalve and effective toholdsaid differential: pressure means including a` cylinder and. piston for controlling the degree of opening.

ofYsaidby-'pass Valve; a spring normally actingto i sure-fa.v .portionV .oa the` .liquidwhich.4 enters .said inlet port; differential:4 pressure means including..-

a cylinder. and.. piston. forv controlling .the degree mallyacting to closesaid by-passvalve and..

effective to .A hold .saidA valve closedA against a pre determined diierential...pressure appliedto. said.V

diiierential pressure: means, .,means.. dening.. a.

plurality of: conduit paths connected inparallel."

in constant communication. with said. inlet port,1 a restriction in-each.conduit path, Vdefining a restricted lopeningof a size. determined by -therate of -iiow desired in. saidpath, .means .providing an open liquid, communication between. said 'inlet portand. thatsideof the pistonof .the differential pressure Vmeans at .which pressure tends. to open'. the. valve, means. .for selectivelyblocking ,a flow throughfallbutoneof said paths, and means for subjecting .the opposite. sideof saidlpiston to the pressure existing beyond the restriction in the a unblocked conduit. path.

11...A.multiple now control valve mechanism v for .usewith'afluid pressure consisting of a constant displacement .pump,.said mechanism includingahousing havingan inlet port andai.

by-pass valve for byfpassing to low pressure .a

portion .of the liquid which enters said inlet porti.`

differential pressure means including Aacvlinder and pistonfor.controllingthe degree of opening of said by-pass valve, a spring Ynormallyrracting to valve closed against a predetermined.differential pressure applied to said differential pressure' means, meansdefning a plurality of conduit" paths.. connected in parallel inconstantcommunication. with said. inlet port, a restriction. in

each .conduit path, means for independently adn justingjsaid restrictions, means providing anV open liquid communication between said inlet. port and'lthat` side of the piston of the differential pressure means at which pressure tends to Y open the valve,.m`eans.for selectively blockingA flowI through all' but one of said. paths, and means. for subjecting, the opposite side of said.'

piston to the pressure existing beyond .the restricportion of` .the liquid which enters said .inlet port,

closet said Icy-pass va'lve'and Veffectiveto hold said va^lvefclosedagainst a predetermined" diierential.i pressureapplied to said differential pressure means,- means defining a* pluralitywf` conduit.

paths'inconstant communication with said inletport, a restriction in each" .conduit path, means"` for.` independently adjusting said restrictions-,f means providing an openliquid communication between said inlet port and'that side of the..pistonofzthe differential pressurevmeanstat which.

pressure ztends. to. .open the valve,i.means for."

i selectively blocking iiow through. all but onefof..v

said paths, and means associated with the coni-r duit'pathsfor 'subjecting the oppositesideofsaid piston'ito s the z pressure .existing beyond '...the.-.:re1.. str-lotion in. the path.. through which flowv isi.oc:Y

curring.

10.1 A multiple flowf controlV valve :mechanism: fo"r`use with a nuid pressure source consisting..

of-a constant displacement-pump, said mechanismf-including. aV .housing .'havingi. an'.v inlet port`l and1a.by'-pass1valve .forzby-passing ato low.l prese.

differential pressure. means including a cylinder and piston for controlling the degree of opening of said'by-passvalve, a spring normally actingto close said by-,pass valve and effective to hold said I valve closedagainst apredetermined differential pressure Vapplied. to said j differential. pressure means,v means defining` a pluralityY of .conduit paths. in constant communication with.V said inlet. port, V-arestrictionineach conduit path defining,V a restricted opening .of a size determined by the.. rate of ow desired insaid path,.means. for independentlyadjustingveach of saidA restrictions means vproviding an. open liquid communication...

betweensaidrinlet port and that side of the. pis.- ton.of...the. differential pressure means at which. pressure tends to open the valve, a .liquidconducting. conduit connected to lsaid differential.. vpressure means at theopposite side ofsaid piston, a.plur.ality of branch. conduits `connecting said last mentioned conduit with said plurality of con duit'paths respectively at points beyond the re. strictions.` therein, valve means. for selectively.

fblockinglow through all but'one of saidconduit..

25 paths, and means operable automatically to block iiow through all of said branch conduits except the one connected to the unblocked conduit path. 13. A multiple ow control valve mechanism for successively maintaining a diierent predetermined rate of ow through each of a plurality -of conduits supplied by a uid pressure source consisting of a constant displacement pump, said mechanism including a housing having an inlet port and a by-pass valve adapted to by-pass to low pressure a portion of the liquid which enters said inlet port, a plurality of parallel conduits in constant communication at one end with said inlet port, and means responsive to the pressure drop incident to flow of liquid through a portion of each conduit as iiow occurs therein for so controlling the degree of opening of said by-pass valve as to maintain said ilow at the predetermined rate for each conduit, said last named means being automatically operable to respond to the pressure drop in only one conduit at a time.

14. A multiple flow control valve mechanism for successively maintaining a different predetermined rate of flow through each of a plurality of conduits supplied by a single uid pressure source consisting of a constant displacement pump, said mechanism including a housing having an inlet port and a by-pass valve adapted to by-pass to low pressure a portion of the liquid which enters said inlet port, a plurality of parallel conduits in constant communication at one end with said inlet port, and means responsive 15. A multiple ow control valve mechanism` for use in controlling the operation of a plurality of successively operable fluid motors from a fluid pressure source consisting of a constant displacement pump, said mechanism including a housing having an inlet port and a by-pass valve for by-passing to low pressure a portion of the liquid which enters said inlet port. differential pressure means including a cylinder and piston for controlling the degree of opening of said by-pass valve, a spring normally acting to close said by-l pass valve and eiective to hold said valve closed against a predetermined differential pressure applied to said differential pressure means, means defining a plurality of conduit paths in constant communication with said inlet port, a restriction in each conduit path, defining a restricted opening of a size determined by the rate of ow desired in said path, means for independently adjusting each of said restrictions means providing an open liquid communication between said inlet port and that side of `the piston. of the differential pressure means at which pressure tends to open the valve, and means for subjecting the opposite side of said piston to the pressure in each of said conduit paths at a point beyond the restriction therein when liquid is flowing in said path at a rate in excess of a predetermined rate of flow.

16. A multiple flow control valve mechanism for use in controlling the operation of a plurality of successively operable iluid motors from a fluid pressure source consisting of a constant displacement pump, said mechanism including a housing having an inlet port and a by-pass valve for by-passing to low pressure a portion of the liquid which enters said inlet port, differential pressure means vincluding a cylinder and piston for controlling the degree of opening of said by-pass valve, a spring normally acting to close said by-pass valve and effective to hold said valve closed against a predetermined differential pressure applied to said differential pressure means. means dening a plurality of conduit paths in constant communication with said inlet port, a restriction in each conduit path, defining a restricted opening of a size determined by the rate of flow desired in said path, means for independently adjusting each of said restrictions means providing an open liquid communication between said inlet port and that side of the piston of the differential pressure means at which pressure tends to open the valve, and means for each conduit path including a normally closed valve operable in response to the existence of a predetermined flow through said path to open and subject the opposite side of said piston to the pressure existing beyond the restriction in the unblocked conduit path.

BENEDICT WELTE.

REFERENCES CITED The following references are of record in the ille of this patent: l

UNITED STATES PATENTS Number Name Date 2,102,865 Vickers Dec. 21, 1937 2,157,707 Keel May 9, 1939 2,259,636 Harrington Oct. 21, 1941 2,263,779 Jeffrey Nov. 25, 1941 2,306,382 Fink Dec. 29, 1942 2,318,851 Griilith May l1, 1943 2,354,634 Griswold July 25, 1944 FOREIGN PATENTS Number Country Date 12,925 Great Britain oi.' 1901 

